1. Field of the Invention
The present invention relates to a view finder for an electronic still camera, which uses a recording medium on which an optical image, formed by a photographing lens, is recorded as a visible image.
2. Description of Related Art
It is known to use a silver halide photographic material as an optical image recording material, since it exhibits a high photosensitivity and resolution, and can be obtained at a low cost. However, a troublesome developing process is required and a visible image cannot be obtained at the time of photographing.
To simplify the developing process, a dry process has been proposed. However, even in the proposed dry process, an instant development is not possible. That is, an image cannot be viewed during the photographing operation. Numerous other non-halide photographic materials are known including electronic photographic materials, diazo photographic materials, free radical photographic materials etc. However, none of these have the same optical properties as those belonging to the silver halide photographic material. Moreover, instant development is not possible using these photographic materials. Note that since electronic photographic materials can be developed using the dry process and that an electrostatic latent image obtained by the exposure can be immediately developed using toner etc., electronic photographic materials have been widely used mainly in copying machines.
In electronic photographing technology, a photographic material from which a recording medium is made has been proposed, wherein the recording medium itself can be directly electronically developed, and a developed visible image thereof can be immediately obtained without any chemical treatment being necessary after exposure. Note that in this specification the recording medium which can be electronically developed is referred to as an electronic development type recording medium.
In Japanese Unexamined Patent Publication No. 5-2280, for example, a recording medium is disclosed, which is comprised of an electrostatic data recording medium and an electric charge holding medium in combination. The electrostatic data recording medium is provided with a photoconductive layer and an inorganic oxide layer, and the charge holding medium is provided with a liquid crystal display element. In this arrangement, if the electrostatic data recording medium is exposed while a voltage is applied between the electrostatic data recording medium and the charge holding medium, electric charges, corresponding to the quantity of light to be incident thereupon, are produced. The intensity of an electric field to be applied to the liquid crystal display element, opposed to the electrostatic data recording medium, varies depending on the electric charges produced. An image corresponding to the distribution of the quantity of light is displayed in the liquid crystal display element, i.e. it has been developed.
Japanese Unexamined Patent Publication No. 5-150251 discloses a dispersive liquid crystal display element in which the image displayed on the liquid crystal display element can be maintained even after the electric field to be applied thereto has been removed.
When an electronic development type recording medium is used with an electronic still camera, it is conventional to make use of either a single lens reflex type view finder, or an optical view finder independent from a photographing optical system. However, in these types of view finders many optical elements are necessary and thus the structure of the camera is complicated.